In the chemical structures of doxorubicin and other anthracycline anticancer drugs, the quinone appears to be a key site of biological action. Various studies suggest that the redox properties of the quinone unit may affect the pattern of antitumor activity and side effects, including cardiotoxicity. Alteration of these redox properties is proposed by the synthesis of anthracycline N-and S-isosteres, with replacement of C equals O by N yields O and S yields O. The proposed N-isosteric aglycone structure contains a hydroxy-substituted phenazine-9, 10-dioxide moiety. Preliminary studies have disclosed weak antileukemic properties in the simple 1-hydroxyphenazine-9, 10-dioxide, suggesting interest in the more elaborated structures proposed.